1. Field of the Invention
The present invention relates to a communication method and system, and more particularly to an ultra wide-band (UWB) transmitted-reference (TR) method and system that provides improved channel estimation in addition to improved Bit Error (BER) and data rates.
2. Description of Related Art
Equalization of the channel impulse response is a major design challenge for ultra-wideband communication systems. The challenge posed by channel estimation is addressed by transmitted-reference (TR) transceivers. The basic building block for a TR modulated waveform is a pair of pulses or doublets that includes a reference pulse “Rf” followed by a transmit pulse “Tr”. The “Tr” pulse is modulated by data while the “Rf” pulse is un-modulated and is used for estimating the wireless channel characteristics. However, the performance of such receivers is considerably limited by the noise-on-noise interference caused by the correlation of noise in “Tr” and “Rf” pulses in low signal-to-noise ratio channels. Furthermore, TR modulation effectively reduces the data rate since for every data pulse, a reference pulse is transmitted simultaneously. In addition, transmission of two or more pulses to represent a data bit dilutes the transmitter power rapidly.
Background information on transmitted-reference transceivers is described in U.S. Patent No. 2001/0053175, entitled “Ultra-Wideband Communications System,” to Hoctor et al., patented Dec. 20, 2001, including the following: “[t]he present invention consists of the combination of two chief features and innovation surrounding each of them. The first of these is known in the art as transmitted-reference (TR). The TR technique is defined as the transmission of two versions of a wideband carrier, one modulated by data and the other unmodulated . . . .”
Accordingly, a need exists for a UWB system and method that provides a new generation of TR transceivers to enable improved channel estimation without diluting the transmitter power by transmitting the reference with every data pulse. The present invention is directed to such a need.